Entia non sunt multiplicanda praeter necessitatem. No more things
should be presumed than is necessary.

This principle of
intellectualeconomy, known as Occam's Razor, is not found in this
form in his writings. Similar expressions can be found, eg
Pluralitas non est ponenda sine necessitate ('Plurality should
not be posited unnecessarily'), in Scriptum in Librum Primum
Sententiarum.